Memory controller and method of operating the same

ABSTRACT

A memory controller may control a memory device. The memory device may be coupled to the memory controller through a channel. The memory controller may include an idle time monitor and a clock signal generator. The idle time monitor may output an idle time interval of the memory device. The idle time interval may be between an end time of a previous operation of the memory device and a start time of a current operation. The clock signal generator may generate a clock signal based on the idle time interval and output the clock signal to the memory device through the channel to perform a current operation.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119(a) toKorean Patent Application Number 10-2019-0149055, filed on Nov. 19,2019, in the Korean Intellectual Property Office, the entire disclosureof which is incorporated herein by reference.

BACKGROUND 1. Technical Field

Various embodiments of the present disclosure generally relate to anelectronic device, and more particularly, to a memory controller and amethod of operating the memory controller.

2. Related Art

Generally, a storage device is a device which stores data under controlof a host device such as a computer, a smartphone, or a smartpad.According to the type of device provided to store data, examples of thestorage device may be classified into a device such as a hard disk drive(HDD) which stores data in a magnetic disk, and a device such as a solidstate drive (SSD) or a memory card which stores data in a semiconductormemory, particularly, a nonvolatile memory.

The storage device may include a memory device in which data is stored,and a memory controller configured to store data in the memory device.Memory devices may be classified into volatile memories and nonvolatilememories. Representative examples of the nonvolatile memories mayinclude a read only memory (ROM), a programmable ROM (PROM), anelectrically programmable ROM (EPROM), an electrically erasableprogrammable ROM (EEPROM), a flash memory, a phase-change random accessmemory (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), aferroelectric RAM (FRAM), etc.

SUMMARY

Various embodiments of the present disclosure are directed to a memorycontroller capable of sequentially increasing or reducing the totalcurrent that is consumed in a plurality of memory devices, and a methodof operating the memory controller.

An embodiment of the present disclosure may provide for a memorycontroller configured to control a memory device. The memory device maybe coupled to the memory controller through a channel. The memorycontroller includes: an idle time monitor configured to output an idletime interval of the memory device, the idle time interval being betweenan end time of a previous operation of the memory device and a starttime of a current operation; and a clock signal generator configured togenerate a clock signal based on the idle time interval and output theclock signal to the memory device through the channel to perform thecurrent operation.

In an embodiment, the clock signal generator may include: a frequencycontroller configured to determine a frequency for generating the clocksignal based on the idle time interval; and a signal generatorconfigured to generate the clock signal based on the determinedfrequency.

In an embodiment, when the idle time interval is greater than athreshold time interval, the frequency controller may determine aninitial frequency for generating the clock signal during an initialfrequency scaling period, and a normal frequency for generating theclock signal during a normal operation period. During the initialfrequency scaling period, the signal generator may generate the clocksignal based on the initial frequency. During the normal operationperiod after the initial frequency scaling period, the signal generatormay generate the clock signal based on the normal frequency.

In an embodiment, a value of the initial frequency may be less than avalue of the normal frequency.

In an embodiment, the frequency controller gradually increases theinitial frequency during the initial frequency scaling period.

In an embodiment, the initial frequency may have a constant value duringthe initial frequency scaling period.

In an embodiment, when the idle time interval is equal to or less than athreshold time interval, the frequency controller may determine a normalfrequency, and the signal generator may generate the clock signal basedon the normal frequency.

In an embodiment, the signal generator may generate a read enable signalas the clock signal.

In an embodiment, the signal generator may generate a data strobe signalas the clock signal.

In an embodiment, the initial frequency scaling period may include afirst initial frequency scaling period and a second initial frequencyscaling period. The frequency controller may determine a first initialfrequency for generating the clock signal during the first initialfrequency scaling period and a second initial frequency for generatingthe clock signal during the second initial frequency scaling period.During the first initial frequency scaling period, the signal generatormay generate the clock signal based on the first initial frequency, thefirst initial frequency being less than the normal frequency. During thesecond initial frequency scaling period, the signal generator maygenerate the clock signal based on the second initial frequency, thesecond initial frequency being less than the normal frequency andgreater than the first initial frequency.

In an embodiment, the first initial frequency may have a constant valueduring the first initial frequency scaling period. The second initialfrequency may gradually increase during the second initial frequencyscaling period.

An embodiment of the present disclosure may provide for a storage deviceincluding: a plurality of memory devices; and a memory controllercoupled with the plurality of memory devices through a plurality ofchannels and configured to control the plurality of memory devices. Whena single memory device among the plurality of memory devices starts anoperation, the memory controller may generate a clock signal based on anidle time interval of the memory device and output the clock signal tothe memory device.

In an embodiment, when the idle time interval is greater than athreshold time interval, the memory controller may generate the clocksignal based on a first frequency during an initial operation period,and generate the clock signal based on a second frequency greater thanthe first frequency during a normal operation period after the initialoperation period.

In an embodiment, the first frequency may be maintained at a constantvalue during the initial operation frequency.

In an embodiment, the first frequency may increase during the initialoperation frequency.

In an embodiment, the clock signal may be any one of a read enablesignal and a data strobe signal.

An embodiment of the present disclosure may provide for a method ofoperating a memory controller, including: determining to start anoperation of a memory device that is idle; determining an idle timeinterval of the memory device; and generating a clock signal based onthe idle time interval to output the clock signal to the memory deviceduring the operation of the memory device.

In an embodiment, generating the clock signal based on the idle timeinterval may include: determining whether the idle time interval isgreater than a threshold time interval; generating the clock signalbased on an initial frequency when the idle time interval is greater thethreshold time interval; and generating the clock signal based on anormal frequency, the normal frequency being greater than the initialfrequency.

In an embodiment, generating the clock signal based on the initialfrequency may include generating the clock signal based on the initialfrequency having a constant value.

In an embodiment, generating the clock signal based on the initialfrequency may include generating the clock signal based on the initialfrequency having a value that gradually increases.

In an embodiment, generating the clock signal based on the initialfrequency may further include: setting initial frequency to a basicfrequency; generating a clock signal based on the initial frequencyuntil a number of cycles of the first clock signal reaches a givennumber; increasing the initial frequency; and generating a second clocksignal based on the increased initial frequency until a number of cyclesof the second clock signal reaches the given number.

In an embodiment, generating the clock signal based on the initialfrequency may include: setting the initial frequency to a basicfrequency; generating the clock signal during a unit time interval,based on the initial frequency; increasing the initial frequency; andgenerating the clock signal during the unit time interval, based on theincreased initial frequency.

An embodiment of the present disclosure may provide for a storage deviceincluding: a plurality of memory devices; and a memory controllercoupled with the plurality of memory devices through a plurality ofchannels, respectively, and configured to control the plurality ofmemory devices. When a selected memory device among the plurality ofmemory devices starts an operation, the memory controller may generate aclock signal based on an idle time interval of at least one unselectedmemory device among the plurality of memory devices and outputs thegenerated clock signal to the selected memory device.

In an embodiment, the at least one unselected memory device is a singleunselected memory device and the idle time interval is that of thesingle unselected memory device. When the idle time interval is greaterthan a threshold time interval, the memory controller may generate theclock signal based on a first frequency during an initial operationperiod, and generate the clock signal based on a second frequency duringa normal operation period after the initial operation period, the secondfrequency being greater than the first frequency.

In an embodiment, the at least one unselected memory device is two ormore unselected memory devices and the idle time interval is a sum ofidle time intervals of the two or more unselected memory devices. Whenthe idle time interval is greater than a threshold time interval, thememory controller may generate the clock signal based on a firstfrequency during an initial operation period, and generate the clocksignal based on a second frequency during a normal operation periodafter the initial operation period, the second frequency being greaterthan the first frequency.

An embodiment of the present disclosure may provide for a storage deviceincluding: a plurality of memory devices; and a memory controllercoupled with the plurality of memory devices through a channel andconfigured to control the plurality of memory devices. When a selectedmemory device among the plurality of memory devices starts an operation,the memory controller may generate a clock signal based on an idle timeinterval of at least one unselected memory device among the plurality ofmemory devices and outputs the generated clock signal to the selectedmemory device.

In an embodiment, the at least one unselected memory device is a singleunselected memory device and the idle time interval is that of thesingle unselected memory device. When the idle time interval is greaterthan a threshold time interval, the memory controller may generate theclock signal based on a first frequency during an initial operationperiod, and generate the clock signal based on a second frequency duringa normal operation period after the initial operation period, the secondfrequency being greater than the first frequency.

In an embodiment, the at least one unselected memory device is two ormore unselected memory devices and the idle time interval is a sum ofidle time intervals of the two or more unselected memory devices. Whenthe idle time interval is greater than a threshold time interval, thememory controller may generate the clock signal based on a firstfrequency during an initial operation period, and generate the clocksignal based on a second frequency during a normal operation periodafter the initial operation period, the second frequency being greaterthan the first frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a storage device in accordancewith an embodiment.

FIG. 2 is a diagram illustrating the configuration of a memory device ofFIG. 1 in accordance with an embodiment.

FIG. 3 is a diagram illustrating a memory cell array of FIG. 2 inaccordance with an embodiment.

FIG. 4 is a circuit diagram illustrating a memory block of a pluralityof memory blocks of FIG. 2 in accordance with an embodiment.

FIG. 5 is a circuit diagram illustrating a memory block of the pluralityof memory blocks of FIG. 2, in accordance with an embodiment.

FIG. 6 is a circuit diagram illustrating a memory block of the pluralityof memory blocks of FIG. 2, in accordance with an embodiment.

FIG. 7 is a diagram illustrating signals which are exchanged between amemory controller and a memory device in accordance with an embodiment.

FIG. 8 is a diagram illustrating memory devices coupled to a pluralityof channels in accordance with an embodiment.

FIG. 9 is a diagram illustrating memory devices coupled to a pluralityof channels in accordance with an embodiment.

FIG. 10 is a diagram for describing a change in entire currentconsumption when memory devices coupled to a plurality of channels startoperations substantially at the same time in accordance with anembodiment.

FIG. 11 is a block diagram illustrating a memory controller inaccordance with an embodiment of the present disclosure.

FIG. 12 is a block diagram illustrating a clock signal generator of FIG.11 in accordance with an embodiment.

FIG. 13 is a flowchart for describing a method of operating a memorycontroller in accordance with an embodiment of the present disclosure.

FIGS. 14A and 14B are timing diagrams for describing a method ofoperating a memory controller in accordance with an embodiment of thepresent disclosure.

FIG. 15 is a flowchart illustrating step S140 of FIG. 13 in accordancewith an embodiment of the present disclosure.

FIGS. 16A and 16B are timing diagrams for describing the embodimentillustrated in FIG. 15.

FIG. 17 is a flowchart illustrating step S140 of FIG. 13 in accordancewith an embodiment of the present disclosure.

FIG. 18 is a timing diagram for describing the embodiment illustrated inFIG. 17.

FIG. 19 is a flowchart illustrating step S140 of FIG. 13 in accordancewith an embodiment of the present disclosure.

FIG. 20 is a timing diagram for describing the embodiment illustrated inFIG. 19.

FIG. 21 is a flowchart illustrating a method of operating a memorycontroller in accordance with an embodiment of the present disclosure.

FIG. 22 is a diagram for describing a method of determining an idle timeaccording to steps S410 and S420 of FIG. 21 in accordance with anembodiment of the present disclosure.

FIG. 23 is a flowchart illustrating a method of operating the memorycontroller in accordance with an embodiment of the present disclosure.

FIG. 24 is a diagram for describing a method of determining an idle timeaccording to steps S510 and S520 of FIG. 23 in accordance with anembodiment of the present disclosure.

FIG. 25 is a diagram illustrating an example of the memory controller ofFIG. 1.

FIG. 26 is a block diagram illustrating a solid state drive (SSD) systemto which the storage device in accordance with an embodiment of thepresent disclosure is applied.

FIG. 27 is a block diagram illustrating a user system to which thestorage device in accordance with an embodiment of the presentdisclosure is applied.

DETAILED DESCRIPTION

Specific structural or functional descriptions in embodiments of thepresent disclosure introduced in this specification or application areonly for description of the embodiments of the present disclosure. Thedescriptions should not be construed as being limited to the embodimentsdescribed in the specification or application.

FIG. 1 is a block diagram illustrating a storage device 50 in accordancewith an embodiment.

Referring to FIG. 1, the storage device 50 may include a memory device100 and a memory controller 200.

The storage device 50 may be a device configured to store data undercontrol of a host 300 such as a cellular phone, a smartphone, an MP3player, a laptop computer, a desktop computer, a game machine, a TV, atablet PC, or an in-vehicle infotainment system.

The storage device 50 may be manufactured as any one of various kinds ofstorage devices depending on a host interface, which is a communicationsystem for communicating with the host 300. For example, the datastorage device 50 may be configured of any one of various kinds ofstorage devices such as an SSD, MMC, eMMC, RS-MMC, or micro-MMC typemultimedia card, an SD, mini-SD, micro-SD type secure digital card, auniversal serial bus (USB) storage device, a universal flash storage(UFS) device, a personal computer memory card international association(PCMCIA) card type storage device, a peripheral componentinterconnection (PCI) card type storage device, a PCI-express (PCI-E)type storage device, a compact flash (CF) card, a smart media card, anda memory stick.

The storage device 50 may be manufactured in the form of any one ofvarious package types. For instance, the storage device 50 may bemanufactured in the form of any one of various package types such as apackage on package (POP) type, a system in package (SIP) type, a systemon chip (SOC) type, a multi-chip package (MCP) type, a chip on board(COB) type, a wafer-level fabricated package (WFP) type, and awafer-level stack package (WSP) type.

The memory device 100 may store data therein. The memory device 100 mayoperate under control of the memory controller 200. The memory device100 may communicate with the memory controller 200 through a channel CH.The memory device 100 may include a memory cell array including aplurality of memory cells configured to store data therein. The memorycell array may include a plurality of memory blocks. Each memory blockmay include a plurality of memory cells. A plurality of memory cells mayform a plurality of pages. In an embodiment, each page may be the unitof storing data in the memory device 100 or reading stored data from thememory device 100. Each memory block may be the unit of erasing data.

In an embodiment, the memory device 100 may be a double data ratesynchronous dynamic random access memory (DDR SDRAM), a low power doubledata rate4 (LPDDR4) SDRAM, a graphics double data rate (GDDR) SDRAM, alow power DDR (LPDDR) SDRAM, a rambus dynamic random access memory(RDRAM), a NAND flash memory, a vertical NAND flash memory, a NOR flashmemory device, a resistive random access memory (RRAM), a phase-changememory (PRAM), a magneto-resistive random access memory (MRAM), aferroelectric random access memory (FRAM), or a spin transfer torquerandom access memory (STT-RAM). In this specification, for the sake ofexplanation, it is assumed that the memory device 100 is a NAND flashmemory.

The memory device 100 may be implemented in a two-dimensional arraystructure or a three-dimensional array structure. Hereinafter, althougha three-dimensional array structure will be described for illustrativepurposes, embodiments of the present disclosure are not limited to thethree-dimensional array structure. Embodiments of the present disclosuremay be applied not only to a flash memory in which a charge storagelayer is formed of a conductive floating gate (FG), but also to a chargetrap flash (CTF) memory in which a charge storage layer is formed of aninsulating layer.

In an embodiment, the memory device 100 may operate in a single-levelcell (SLC) manner of storing one data bit in each memory cell.Alternatively, the memory device 100 may operate in a manner of storingat least two data bits in each memory cell. For example, the memorydevice 100 may operate in a multi-level cell (MLC) manner of storing twodata bits in each memory cell, a triple-level cell (TLC) manner ofstoring three data bits in each memory cell, or a quad-level cell (QLC)manner of storing four data bits in each memory cell.

The memory device 100 may receive a command and an address from thememory controller 200 through the channel CH and access an area of thememory cell array that is selected by the address. In other words, thememory device 100 may perform an operation corresponding to the commandon the area selected by the address. For example, the memory device 100may perform a write operation (or a program operation), a readoperation, or an erase operation, in response to a received command. Forexample, when a program command is received, the memory device 100 mayprogram data in an area selected by an address. If a read command isreceived, the memory device 100 may read data from an area selected byan address. If an erase command is received, the memory device 100 mayerase data from an area selected by an address.

In an embodiment, the memory device 100 may be provided as a pluralityof memory devices. In other words, a plurality of memory devices may beincluded in the storage device 50.

The plurality of memory devices may be coupled with the memorycontroller 200 through channels CH, and communicate with the memorycontroller 200 through the channels CH. For example, the memorycontroller 200 may instruct each of the plurality of memory devices toperform an operation. Each of the plurality of memory devices mayperform an operation corresponding to the instruction of the memorycontroller 200. Furthermore, each of the plurality of memory devices mayoutput a result of performing the corresponding operation to the memorycontroller 200.

The memory controller 200 may control overall operations of the storagedevice 50.

When a power supply voltage is applied to the storage device 50, thememory controller 200 may execute firmware (FW). In the case where thememory device 100 is a flash memory device, the memory controller 200may execute firmware such as a flash translation layer (FTL) forcontrolling communication between the host 300 and the memory device100.

In an embodiment, the memory controller 200 may include firmware whichreceives data and a logical block address (LBA) from the host 300, andtranslates the LBA into a physical block address (PBA) indicatingaddresses of memory cells in which data is to be stored, the memorycells being included in the memory device 100. The memory controller 200may store, in a buffer memory, a logical-physical address mapping tableindicating mapping relationship between logical block addresses LBA andphysical block addresses PBA.

The memory controller 200 may control the memory device 100 to perform aprogram operation, a read operation, or an erase operation in responseto a request from the host 300. For example, if a program request isreceived from the host 300, the memory controller 200 may change theprogram request into a program command, and provide the program command,a PBA, and data to the memory device 100. If a read request along withan LBA is received from the host 300, the memory controller 200 maychange a read request into a read command, select a PBA corresponding tothe LBA, and provide the read command and the PBA to the memory device100. If an erase request along with an LBA is received from the host300, the memory controller 200 may change the erase request into anerase command, select a PBA corresponding to the LBA, and provide theerase command and the PBA to the memory device 100.

In an embodiment, the memory controller 200 may autonomously generate aprogram command, an address, and data without a request from the host300, and transmit them to the memory device 100. For example, the memorycontroller 200 may provide a command, an address, and data to the memorydevice 100 to perform background operations such as a program operationfor wear leveling, and a program operation for garbage collection.

In an embodiment, the storage device 50 may further include a buffermemory (not illustrated). The memory controller 200 may control dataexchange between the host 300 and the buffer memory (not illustrated).Alternatively, the memory controller 200 may temporarily store systemdata for controlling the memory device 100 in the buffer memory. Forexample, the memory controller 200 may temporarily store data input fromthe host 300 in the buffer memory, and thereafter transmit the datatemporarily stored in the buffer memory to the memory device 100.

In various embodiments, the buffer memory may be used as an operatingmemory or a cache memory of the memory controller 200. The buffer memorymay store codes or commands to be executed by the memory controller 200.Alternatively, the buffer memory may store data to be processed by thememory controller 200.

In an embodiment, the buffer memory may be embodied using an SRAM or aDRAM such as a double data rate synchronous dynamic random access memory(DDR SDRAM), a DDR4 SDRAM, a low power double data rate4 (LPDDR4) SDRAM,a graphics double data rate (GDDR) SDRAM, a low power DDR (LPDDR), or arambus dynamic random access memory (RDRAM).

In various embodiments, the buffer memory may be provided outside thestorage device 50. In this case, volatile memory devices providedoutside the storage device 50 may function as the buffer memory.

In an embodiment, the memory controller 200 may control at least two ormore memory devices. In this case, the memory controller 200 may controlthe memory devices in an interleaving manner so as to enhance theoperating performance.

The host 300 may communicate with the storage device 50 using at leastone of various communication methods such as universal serial bus (USB),serial AT attachment (SATA), serial attached SCSI (SAS), high speedinterchip (HSIC), small computer system interface (SCSI), peripheralcomponent interconnection (PCI), PCI express (PCIe), nonvolatile memoryexpress (NVMe), universal flash storage (UFS), secure digital (SD),multi-media card (MMC), embedded MMC (eMMC), dual in-line memory module(DIMM), registered DIMM (RDIMM), and load reduced DIMM (LRDIMM)communication methods.

FIG. 2 is a diagram illustrating the configuration of the memory device100 of FIG. 1 in accordance with an embodiment.

Referring to FIG. 2, the memory device 100 may include a memory cellarray 110, a peripheral circuit 120, and a control logic 130.

The memory cell array 110 may include a plurality of memory blocks BLK1to BLKz. The plurality of memory blocks BLK1 to BLKz are coupled to anaddress decoder 121 through row lines RL. The plurality of memory blocksBLK1 to BLKz may be coupled to a page buffer group 123 through bit linesBL1 to BLn. Each of the memory blocks BLK1 to BLKz may include aplurality of memory cells. In an embodiment, the plurality of memorycells may be nonvolatile memory cells. Memory cells coupled to the sameword line may be defined as one page. Hence, each memory block mayinclude a plurality of pages.

The row lines RL may include at least one source select line, aplurality of word lines, and at least one drain select line.

Each of the memory cells included in the memory cell array 110 may beformed of a single level cell (SLC) capable of storing a single databit, a multi-level cell (MLC) capable of storing two data bits, atriple-level cell (TLC) capable of storing three data bits, or aquad-level cell (QLC) capable of storing four data bits.

The peripheral circuit 120 may perform a program operation, a readoperation, or an erase operation on a selected area of the memory cellarray 110 under control of the control logic 130. The peripheral circuit120 may drive the memory cell array 110. For example, the peripheralcircuit 120 may apply various operating voltages to the row lines RL andthe bit lines BL1 to BLn or discharge the applied voltages, undercontrol of the control logic 130.

The peripheral circuit 120 may include the address decoder 121, avoltage generator 122, the page buffer group 123, a column decoder 124,an input/output circuit 125, and a sensing circuit 126.

The address decoder 121 is coupled to the memory cell array 110 throughthe row lines RL. The row lines RL may include at least one sourceselect line, a plurality of word lines, and at least one drain selectline. In an embodiment, the word lines may include normal word lines anddummy word lines. In an embodiment, the row lines RL may further includea pipe select line.

The address decoder 121 may decode a row address RADD received from thecontrol logic 130. The address decoder 121 may select at least onememory block of the memory blocks BLK1 to BLKz in response to thedecoded address. The address decoder 121 may select at least one wordline of the selected memory block in response to the decoded address sothat voltages generated from the voltage generator 122 are applied tothe at least one word line.

For example, during a program operation, the address decoder 121 mayapply a program voltage to a selected word line and apply a program passvoltage having a level lower than that of the program voltage tounselected word lines. During a program verify operation, the addressdecoder 121 may apply a verify voltage to a selected word line and applya verify pass voltage higher than the verify voltage to unselected wordlines. During a read operation, the address decoder 121 may apply a readvoltage to a selected word line and apply a read pass voltage higherthan the read voltage to unselected word lines.

In an embodiment, an erase operation of the memory device 100 may beperformed on a memory block basis. During an erase operation, theaddress decoder 121 may select one memory block in response to a decodedaddress. During the erase operation, the address decoder 121 may apply aground voltage to word lines coupled to the selected memory block.

The voltage generator 122 may operate under control of the control logic130. The voltage generator 122 may generate a plurality of voltagesusing an external supply voltage supplied to the memory device 100. Indetail, the voltage generator 122 may generate various operatingvoltages Vop to be used for a program operation, a read operation, andan erase operation in response to an operating signal OPSIG. Forexample, the voltage generator 122 may generate a program voltage, averify voltage, a pass voltage, a read voltage, an erase voltage, and soforth under control of the control logic 130.

In an embodiment, the voltage generator 122 may generate an internalsupply voltage by regulating the external supply voltage. The internalsupply voltage generated from the voltage generator 122 may be used asan operating voltage of the memory device 100.

In an embodiment, the voltage generator 122 may generate a plurality ofvoltages using an external power supply voltage or an internal powersupply voltage.

For example, the voltage generator 122 may include a plurality ofpumping capacitors for receiving the internal supply voltage andgenerate a plurality of voltages by selectively activating the pluralityof pumping capacitors under control of the control logic 130.

The generated voltages may be supplied to the memory cell array 110 bythe address decoder 121.

The page buffer group 123 may include first to n-th page buffers PB1 toPBn. The first to n-th page buffers PB1 to PBn are coupled to the memorycell array 110 through the first to n-th bit lines BL1 to BLn,respectively. The first to n-th page buffers PB1 to PBn may operateunder control of the control logic 130. In detail, the first to n-thpage buffers PB1 to PBn may operate in response to page buffer controlsignals PBSIGNALS. For instance, the first to n-th page buffers PB1 toPBn may temporarily store data received through the first to n-th bitlines BL1 to BLn, or sense voltages or currents of the first to n-th bitlines BL1 to BLn during a read operation or a verify operation.

In detail, during a program operation, the first to n-th page buffersPB1 to PBn may transmit data DATA received through the input/outputcircuit 125 to selected memory cells through the first to n-th bit linesBL1 to BLn when a program voltage is applied to a selected word line.The memory cells in the selected page are programmed based on thetransmitted data DATA. During a program verify operation, the first ton-th page buffers PB1 to PBn may read page data by sensing voltages orcurrents received from selected memory cells through the first to n-thbit lines BL1 to BLn.

During a read operation, the first to n-th page buffers PB1 to PBn mayread data DATA from memory cells of a selected page through the first ton-th bit lines BL1 to BLn, and output the read data DATA to the datainput/output circuit 125 under control of the column decoder 124.

During an erase operation, the first to n-th page buffers PB1 to PBn mayfloat the first to n-th bit lines BL1 to BLn or apply erase voltagesthereto.

The column decoder 124 may transmit data between the input/outputcircuit 125 and the page buffer group 123 in response to a columnaddress CADD. For example, the column decoder 124 may exchange data withthe first to n-th page buffers PB1 to PBn through data lines DL orexchange data with the input/output circuit 125 through column lines CL.

The input/output circuit 125 may transmit, to the control logic 130, acommand CMD or an address ADDR received from a memory controller (e.g.,the memory controller 200 of FIG. 1), or may exchange data DATA with thecolumn decoder 124.

During a read operation or a verify operation, the sensing circuit 126may generate a reference current in response to an enable bit signalVRYBIT, and may compare a sensing voltage VPB received from the pagebuffer group 123 with a reference voltage generated by the referencecurrent and output a pass signal PASS or a fail signal FAIL.

The control logic 130 may output an operating signal OPSIG, a rowaddress RADD, page buffer control signals PBSIGNALS, and an enable bitsignal VRYBIT in response to a command CMD and an address ADD, and thuscontrol the peripheral circuit 120. For example, the control logic 130may control a read operation of a selected memory block in response to asub-block read command and an address. Furthermore, the control logic130 may control an erase operation of a selected sub-block included in aselected memory block, in response to a sub-block erase command and anaddress. In addition, the control logic 130 may determine whether atarget memory cell has passed a verification during a verify operationin response to a pass signal PASS or a fail signal FAIL.

Each of the memory cells included in the memory cell array 110 may beprogrammed to any one programmed state among a plurality of programmedstates depending on data to be stored in the corresponding memory cell.A target programmed state of a memory cell may be determined to be anyone of the plurality of programmed states depending on data to be storedtherein.

FIG. 3 is a diagram illustrating the memory cell array 110 of FIG. 2 inaccordance with an embodiment.

Referring to FIG. 3, the memory cell array 110 may include a pluralityof memory blocks BLK1 to BLKz. Each memory block may have athree-dimensional structure. Each memory block may include a pluralityof memory cells stacked on a substrate. The memory cells are arranged ina +X direction, a +Y direction, and a +Z direction. The structure ofeach memory block will be described in more detail with reference toFIGS. 4 and 5.

FIG. 4 is a circuit diagram illustrating a memory block BLKa of thememory blocks BLK1 to BLKz of FIG. 2 in accordance with an embodiment.

Referring to FIG. 4, the memory block BLKa may include a plurality ofcell strings CS11 to CS1 m and CS21 to CS2 m. In an embodiment, each ofthe cell strings CS11 to CS1 m and CS21 to CS2 m may be formed in a ‘U’shape. In the memory block BLKa, m cell strings may be arranged in a rowdirection (i.e., the +X direction). In FIG. 4, two cell strings areillustrated as being arranged in a column direction (i.e., the +Ydirection). However, this illustration is made only for convenience ofdescription, and it will be understood that three or more cell stringsmay be arranged in the column direction.

Each of the plurality of cell strings CS11 to CS1 m and CS21 to CS2 mmay include at least one source select transistor SST, first to n-thmemory cells MC1 to MCn, a pipe transistor PT, and at least one drainselect transistor DST.

The select transistors SST and DST and the memory cells MC1 to MCn mayhave similar structures, respectively. In an embodiment, each of theselect transistors SST and DST and the memory cells MC1 to MCn mayinclude a channel layer, a tunneling insulating layer, a charge storagelayer, and a blocking insulating layer. In an embodiment, a pillar forproviding the channel layer may be provided in each cell string. In anembodiment, a pillar for providing at least one of the channel layer,the tunneling insulating layer, the charge storage layer, and theblocking insulating layer may be provided in each cell string.

The source select transistor SST of each cell string is coupled betweenthe common source line CSL and the memory cells MC1 to MCp.

In an embodiment, source select transistors of cell strings arranged inthe same row are coupled to a source select line extending in a rowdirection, and source select transistors of cell strings arranged indifferent rows are coupled to different source select lines. In FIG. 4,source select transistors of the cell strings CS11 to CS1 m in a firstrow are coupled to a first source select line SSL1. Source selecttransistors of the cell strings CS21 to CS2 m in a second row arecoupled to a second source select line SSL2.

In an embodiment, the source select transistors of the cell strings CS11to CS1 m and CS21 to CS2 m may be coupled in common to a single sourceselect line.

The first to n-th memory cells MC1 to MCn in each cell string arecoupled between the source select transistor SST and the drain selecttransistor DST.

The first to n-th memory cells MC1 to MCn may be divided into first top-th memory cells MC1 to MCp and p+1-th to n-th memory cells MCp+1 toMCn. The first to p-th memory cells MC1 to MCp are successively arrangedin a direction opposite to the +Z direction and are coupled in seriesbetween the source select transistor SST and the pipe transistor PT. Thep+1-th to n-th memory cells MCp+1 to MCn are successively arranged inthe +Z direction and are coupled in series between the pipe transistorPT and the drain select transistor DST. The first to p-th memory cellsMC1 to MCp and the p+1-th to n-th memory cells MCp+1 to MCn are coupledto each other through the pipe transistor PT. The gates of the first ton-th memory cells MC1 to MCn of each cell string are coupled to first ton-th word lines WL1 to WLn, respectively.

Respective gates of the pipe transistors PT of the cell strings arecoupled to a pipeline PL.

The drain select transistor DST of each cell string is coupled betweenthe corresponding bit line and the memory cells MCp+1 to MCn. The cellstrings arranged in the row direction are coupled to drain select linesextending in the row direction. Drain select transistors of the cellstrings CS11 to CS1 m in the first row are coupled to a first drainselect line DSL1. Drain select transistors of the cell strings CS21 toCS2 m in the second row are coupled to a second drain select line DSL2.

Cell strings arranged in the column direction may be coupled to bitlines extending in the column direction. In FIG. 4, cell strings CS11and CS21 in a first column are coupled to a first bit line BL1. Cellstrings CS1 m and CS2 m in an m-th column are coupled to an m-th bitline BLm.

Memory cells coupled to the same word line in cell strings arranged inthe row direction form a single page. For example, memory cells coupledto the first word line WL1, among the cell strings CS11 to CS1 m in thefirst row, form a single page. Memory cells coupled to the first wordline WL1, among the cell strings CS21 to CS2 m in the second row, formanother single page. When any one of the drain select lines DSL1 andDSL2 is selected, corresponding cell strings arranged in the directionof a single row may be selected. When any one of the word lines WL1 toWLn is selected, a corresponding single page may be selected from amongthe selected cell strings.

In an embodiment, even bit lines and odd bit lines may be provided inlieu of the first to m-th bit lines BL1 to BLm. Even-number cell stringsof the cell strings CS11 to CS1 m or CS21 to CS2 m arranged in the rowdirection may be coupled to respective even bit lines. Odd-number cellstrings of the cell strings CS11 to CS1 m or CS21 to CS2 m arranged inthe row direction may be coupled to respective odd bit lines.

In an embodiment, at least one of the first to n-th memory cells MC1 toMCn may be used as a dummy memory cell. For example, at least one ormore dummy memory cells may be provided to reduce an electric fieldbetween the source select transistor SST and the memory cells MC1 toMCp. Alternatively, at least one or more dummy memory cells may beprovided to reduce an electric field between the drain select transistorDST and the memory cells MCp+1 to MCn. As the number of dummy memorycells is increased, the reliability in operation of the memory blockBLKa may be increased, while the size of the memory block BLKa may beincreased. As the number of dummy memory cells is reduced, the size ofthe memory block BLKa may be reduced, but the reliability in operationof the memory block BLKa may be reduced.

To efficiently control the at least one dummy memory cells, each of thedummy memory cells may have a required threshold voltage. Before orafter an erase operation on the memory block BLKa is performed, programoperations may be performed on all or some of the dummy memory cells. Inthe case where an erase operation is performed after a program operationhas been performed, the dummy memory cells may have required thresholdvoltages by controlling voltages to be applied to the dummy word linescoupled to the respective dummy memory cells.

FIG. 5 is a circuit diagram illustrating a memory block BLKb of thememory blocks BLK1 to BLKz of FIG. 2, in accordance with an embodiment.

Referring to FIG. 5, the memory block BLKb may include a plurality ofcell strings CS11′ to CS1 m′ and CS21′ to CS2 m′. Each of the cellstrings CS11′ to CS1 m′ and CS21′ to CS2 m′ extends in the +Z direction.Each of the cell strings CS11′ to CS1 m′ and CS21′ to CS2 m′ may includeat least one source select transistor SST, first to n-th memory cellsMC1 to MCn, and at least one drain select transistor DST which arestacked on a substrate (not shown) provided in a lower portion of thememory block BLKb.

The source select transistor SST of each cell string is coupled betweenthe common source line CSL and the memory cells MC1 to MCn. The sourceselect transistors of cell strings arranged in the same row are coupledto the same source select line. Source select transistors of the cellstrings CS11′ to CS1 m′ arranged in a first row may be coupled to afirst source select line SSL1. Source select transistors of the cellstrings CS21′ to CS2 m′ arranged in a second row may be coupled to asecond source select line 55L2. In an embodiment, source selecttransistors of the cell strings CS11′ to CS1 m′ and CS21′ to CS2 m′ maybe coupled in common to a single source select line.

The first to n-th memory cells MC1 to MCn in each cell string arecoupled in series between the source select transistor SST and the drainselect transistor DST. Gates of the first to n-th memory cells MC1 toMCn are respectively coupled to first to n-th word lines WL1 to WLn.

The drain select transistor DST of each cell string is coupled betweenthe corresponding bit line and the memory cells MC1 to MCn. Drain selecttransistors of cell strings arranged in the row direction may be coupledto drain select lines extending in the row direction. Drain selecttransistors of the cell strings CS11′ to CS1 m′ in the first row arecoupled to a first drain select line DSL1. Drain select transistors ofthe cell strings CS21′ to CS2 m′ in the second row may be coupled to asecond drain select line DSL2.

Consequently, the memory block BLKb of FIG. 5 may have an equivalentcircuit similar to that of the memory block BLKa of FIG. 4 except that apipe transistor PT of FIG. 4 is excluded from each cell string of thememory block BLKb of FIG. 5.

In an embodiment, even bit lines and odd bit lines may be provided inlieu of the first to m-th bit lines BL1 to BLm. Even-number cell stringsamong the cell strings CS11′ to CS1 m′ or CS21′ to CS2 m′ arranged inthe row direction may be coupled to the respective even bit lines, andodd-number cell strings among the cell strings CS11′ to CS1 m′ or CS21′to CS2 m′ arranged in the row direction may be coupled to the respectiveodd bit lines.

In an embodiment, at least one of the first to n-th memory cells MC1 toMCn may be used as a dummy memory cell. For example, at least one ormore dummy memory cells may be provided to reduce an electric fieldbetween the source select transistor SST and the memory cells MC1 toMCn. Alternatively, at least one or more dummy memory cells may beprovided to reduce an electric field between the drain select transistorDST and the memory cells MC1 to MCn. As the number of dummy memory cellsis increased, the reliability in operation of the memory block BLKb maybe increased, while the size of the memory block BLKb may be increased.As the number of dummy memory cells is reduced, the size of the memoryblock BLKb may be reduced, but the reliability in operation of thememory block BLKb may be reduced.

To efficiently control the at least one dummy memory cells, each of thedummy memory cells may have a required threshold voltage. Before orafter an erase operation on the memory block BLKb is performed, programoperations may be performed on all or some of the dummy memory cells. Inthe case where an erase operation is performed after a program operationhas been performed, the dummy memory cells may have required thresholdvoltages by controlling voltages to be applied to the dummy word linescoupled to the respective dummy memory cells.

FIG. 6 is a circuit diagram illustrating a memory block BLKc of thememory blocks BLK1 to BLKz included in the memory cell array 110 of FIG.2, in accordance with an embodiment.

Referring to FIG. 6, the memory block BLKc includes a plurality of cellstrings CS1 to CSm. The plurality of cell strings CS1 to CSm may berespectively coupled to a plurality of bit lines BL1 to BLm. Each of thecell strings CS1 to CSm includes at least one source select transistorSST, first to n-th memory cells MC1 to MCn, and at least one drainselect transistor DST.

The select transistors SST and DST and the memory cells MC1 to MCn mayhave similar structures, respectively. In an embodiment, each of theselect transistors SST and DST and the memory cells MC1 to MCn mayinclude a channel layer, a tunneling insulating layer, a charge storagelayer, and a blocking insulating layer. In an embodiment, a pillar forproviding the channel layer may be provided in each cell string. In anembodiment, a pillar for providing at least one of the channel layer,the tunneling insulating layer, the charge storage layer, and theblocking insulating layer may be provided in each cell string.

The source select transistor SST of each cell string is coupled betweenthe common source line CSL and the memory cells MC1 to MCn.

The first to n-th memory cells MC1 to MCn in each cell string arecoupled between the source select transistor SST and the drain selecttransistor DST.

The drain select transistor DST of each cell string is coupled betweenthe corresponding bit line and the memory cells MC1 to MCn.

Memory cells coupled to the same word line may form a single page. Thecell strings CS1 to CSm may be selected by selecting the drain selectline DSL. When any one of the word lines WL1 to WLn is selected, acorresponding single page may be selected from among the selected cellstrings.

In an embodiment, even bit lines and odd bit lines may be provided inlieu of the first to m-th bit lines BL1 to BLm. Even-number cell stringsof the cell strings CS1 to CSm may be coupled to the respective even bitlines, and odd-number cell strings may be coupled to the respective oddbit lines.

As illustrated in FIGS. 3 to 5, the memory cell array 110 of the memorydevice 100 may be formed of a memory cell array having athree-dimensional structure. Furthermore, as illustrated in FIG. 6, thememory cell array 110 of the memory device 100 may be formed of a memorycell array having a two-dimensional structure.

FIG. 7 is a diagram illustrating signals which are exchanged between amemory controller 200 and a memory device 100 in accordance with anembodiment. Referring to FIG. 7, the memory controller 200 and thememory device 100 may exchange one or more signals DQ[7:0] eachindicating a command, data, and an address through a data pad.Furthermore, the memory controller 200 and the memory device 100 mayexchange a data strobe signal DQS through a data strobe pad. The memorydevice 100 may receive a chip enable signal CE #, a write enable signalWE #, a read enable signal RE #, an address latch enable signal ALE, acommand latch enable signal CLE, a write protection signal WP #, etc.Also, the memory device 100 may output a ready/busy signal RB through aready/busy pad.

To perform a program operation of the memory device 100, the memorycontroller 200 may output a data strobe signal DQS through the datastrobe pad. In synchronization with the data strobe signal DQS outputthrough the data strobe pad, the memory controller 200 may output aprogram command, an address, and program data through the data pad.

To perform a read operation of the memory device 100, the memorycontroller 200 may output a read enable signal RE # through a readenable pad. In response to the read enable signal RE #, the memorydevice 100 may output a data strobe signal DQS. In synchronization withthe data strobe signal DQS, the memory device 100 may output read datathrough the data pad.

During a program operation of the memory device 100, the memorycontroller 200 may output a data strobe signal DQS to the memory device100, and output program data to the memory device 100 through the datapad. During a read operation of the memory device 100, the memory device100 may output a data strobe signal DQS to the memory controller 200,and output read data to the memory controller 200 through the data pad.

FIG. 8 is a diagram illustrating memory devices coupled to a pluralityof channels in accordance with an embodiment.

FIG. 8 illustrates the case where a plurality of memory devices includedin a storage device (e.g., the storage device 50 of FIG. 1) are coupledto a memory controller 200. In FIG. 8, it is assumed that the pluralityof memory devices coupled to the memory controller 200 include first tofourth memory devices 100_1 to 100_4, i.e., a total of four memorydevices. However, embodiments of the present disclosure are not limitedthereto, and the number of memory devices coupled to the memorycontroller 200 may vary according to embodiments.

In an embodiment, a plurality of memory devices may be coupled to thememory controller 200. For example, the memory controller 200 may becoupled to the first memory device 100_1 through a first channel CH1,the second memory device 100_2 through a second channel CH2, the thirdmemory device 100_3 through a third channel CH3, and the fourth memorydevice 100_4 through a fourth channel CH4.

The memory controller 200 may generate a command corresponding to arequest received from a host (e.g., the host 300 of FIG. 1) and outputthe command to any one of the first to fourth memory devices 100_1 to100_4. The request received from the host 300 may be a program request,a read request, or an erase request for any one of the first to fourthmemory devices 100_1 to 100_4.

For example, if a request received from the host 300 is a read requestfor the first memory device 100_1, the memory controller 200 maygenerate a command corresponding to the read request and output thecommand to the first memory device 100_1 through the first channel CH1.Here, the memory controller 200 may output not only the commandcorresponding to the read request but also an address corresponding tothe read request to the first memory device 100_1 through the firstchannel CH1.

If a request received from the host 300 is a program request for thesecond memory device 100_2, the memory controller 200 may generate acommand corresponding to the program request and output the command tothe second memory device 100_2 through the second channel CH2. Here, anaddress and data corresponding to the program request may also be outputto the second memory device 100_2 through the second channel CH2.

As described above, the memory controller 200 may generate one or moreof a command, an address, and data corresponding to a request receivedfrom the host 300. If the request is a request for the first memorydevice 100_1, the first channel 1 may be used to output the generatedone or more of command, address, and data. If the request is a requestfor the second memory device 100_2, the second channel 2 may be used. Ifthe request is a request for the third memory device 100_3, the thirdchannel 3 may be used. If the request is a request for the fourth memorydevice 100_4, the fourth channel CH4 may be used.

As such, the memory controller 200 may communicate with a plurality ofmemory devices through a plurality of channels.

In an embodiment, in the case where the plurality of memory devicesperform operations corresponding to commands received through thechannels, respectively, current consumption may be increased.Particularly, if the plurality of memory devices start operationssubstantially at the same time, the entire current consumption of theplurality of memory devices may be rapidly increased. In the case theentire current consumption is rapidly increased, a noise occurs on avoltage source, thereby deteriorating the operational reliability of thestorage device 50. For example, the plurality of memory devices mayshare a single voltage source, and thus such a relatively high increaseof the entire current consumption by the plurality of memory devices maylead to an occurrence of a noise on the voltage source.

In the memory controller 200 according to an embodiment of the presentdisclosure, when each of the memory devices 100_1 to 100_4 starts anoperation, an initial frequency of a clock signal output may becontrolled based on an idle time of each of the memory devices 100_1 to100_4. In an embodiment, the clock signal that is output from the memorycontroller 200 may be a read enable signal RE # which is output during aread operation, or a data strobe signal DQS which is output during aprogram operation. In the memory controller 200 in accordance with anembodiment of the present disclosure, if the idle time of a memorydevice 100_1, 100_2, 100_3, or 100_4 exceeds a threshold time, a clocksignal to be output to the memory device may be generated based on aninitial frequency (or initial operation frequency) less than a normalfrequency during an initial frequency scaling period. In an embodiment,when the idle time of a memory device 100_1, 100_2, 100_3, or 100_4exceeds a threshold time, the memory controller 200 may generate a clocksignal having an initial frequency during an initial frequency scalingperiod, the initial frequency being less than a normal frequency. If theinitial frequency scaling period has passed and the process enters anormal operation period, the memory controller may generate clocksignals to be output to the memory devices 100_1 to 100_4 based on thenormal frequency. Therefore, if the plurality of memory devices 100_1 to100_4 start operations substantially at the same time, the entirecurrent consumption of the storage device 50 may be prevented fromrapidly increasing by reducing an initial operation frequency of each ofthe clock signals output from the memory devices 100_1 to 100_4 duringthe initial frequency scaling period compared to the normal frequency.

FIG. 9 is a diagram illustrating memory devices coupled to a pluralityof channels in accordance with an embodiment.

Referring to FIGS. 8 and 9, first to eighth memory devices 100_1 to100_8 of FIG. 9 may be coupled to the memory controller 200 throughfirst to fourth channels CH1 to CH4, in a similar manner to thatdescribed with reference to FIG. 8. However, FIG. 8 illustrates the casewhere a single memory device is coupled to each channel. FIG. 9illustrates the case where two memory devices are coupled to eachchannel. In another embodiment, three or more memory devices may becoupled to each channel.

In an embodiment, the first memory device 100_1 is coupled to the firstchannel CH1 through a first way WAY1, and the second memory device 100_2is coupled to the first channel CH1 through a second way WAY2. The firstand second memory devices 100_1 and 100_2 may be coupled to the memorycontroller 200 through the first channel CH1. The third memory device100_2 is coupled to the second channel CH2 through a third way WAY3, andthe fourth memory device 100_4 is coupled to the second channel CH2through a fourth way WAY4. Hence, the third and fourth memory devices100_3 and 100_4 may be coupled to the memory controller 200 through thesecond channel CH2.

In an embodiment, the fifth memory device 100_5 is coupled to the thirdchannel CH3 through a fifth way WAY5, and the sixth memory device 100_6is coupled to the third channel CH3 through a sixth way WAY6. Hence, thefifth and sixth memory devices 100_5 and 100_6 may be coupled to thememory controller 200 through the third channel CH3. The seventh memorydevice 100_7 is coupled to the fourth channel CH4 through a seventh wayWAY7, and the eighth memory device 100_8 is coupled to the fourthchannel CH4 through an eighth way WAY8. Hence, the seventh and eighthmemory devices 100_7 and 100_8 may be coupled to the memory controller200 through the fourth channel CH4.

In an embodiment, the memory controller 200 may generate a commandcorresponding to a request from a host (e.g., the host 300 of FIG. 1)and output the command to any one of the first to eighth memory devices100_1 to 100_8. The request received from the host 300 may be a programrequest, a read request, or an erase request for any one of the first toeighth memory devices 100_1 to 100_8.

For example, if a request received from the host 300 is a read requestfor the first memory device 100_1, the memory controller 200 maygenerate a command corresponding to the read request and output thecommand to the first memory device 100_1 through the first channel CH1.Here, the memory controller 200 may output not only the commandcorresponding to the read request but also an address corresponding tothe read request to the first memory device 100_1 through the firstchannel CH1.

If a request received from the host 300 is a program request for thesecond memory device 100_2, the memory controller 200 may generate acommand corresponding to the program request and output the command tothe second memory device 100_2 through the first channel CH1. Here, anaddress and data corresponding to the program request may also be outputto the second memory device 100_2 through the first channel CH1.

As described above, if a request received from the host 300 is a requestfor the first memory device 100_1 or the second memory device 100_2, thememory controller 200 may output one or more of a command, an address,and data corresponding to the request from the host 300 to the firstmemory device 100_1 or the second memory device 100_2 through the firstchannel CH1. If a request received from the host 300 is a request forthe third memory device 100_3 or the fourth memory device 100_4, thememory controller 200 may output one or more of a command, an address,and data corresponding to the request from the host 300 to the thirdmemory device 100_3 or the fourth memory device 100_4 through the secondchannel CH2.

In an embodiment, if a request received from the host 300 is a requestfor the fifth memory device 100_5 or the sixth memory device 100_6, thememory controller 200 may output one or more of a command, an address,and data corresponding to the request from the host 300 to the fifthmemory device 100_5 or the sixth memory device 100_6 through the thirdchannel CH3. If a request received from the host 300 is a request forthe seventh memory device 100_7 or the eighth memory device 100_8, thememory controller 200 may output one or more of a command, an address,and data corresponding to the request from the host 300 to the seventhmemory device 100_7 or the eighth memory device 100_8 through the fourthchannel CH4.

In the same manner as described with reference to FIG. 8, the memorycontroller 200 may communicate with a plurality of memory devicesthrough a plurality of channels.

In the memory controller 200 in accordance with an embodiment of thepresent disclosure, when each of the memory devices 100_1 to 100_8starts an operation, an initial frequency of a clock signal output maybe controlled based on an idle time of each of the memory devices 100_1to 100_8. In an embodiment, the clock signal that is output from thememory controller 200 may be a read enable signal RE # which is outputthrough the read enable pad during a read operation, or a data strobesignal DQS which is output through the DQS pad during a programoperation. In the memory controller 200 in accordance with an embodimentof the present disclosure, if the idle time of one of the memory devices100_1 to 100_8 exceeds a threshold time, a clock signal to be output tothe memory device may be generated based on an initial frequency lessthan a normal frequency during an initial frequency scaling period. Ifthe initial frequency scaling period has passed and the process enters anormal operation period, the memory controller 200 may generate clocksignals to be output to the memory devices 100_1 to 100_8 based on thenormal frequency. Therefore, if the plurality of memory devices 100_1 to100_8 start operations substantially at the same time, the entirecurrent consumption of the storage device 50 may be prevented fromrapidly increasing by reducing the initial operation frequency of eachof the clock signals output from the memory devices 100_1 to 100_8during the initial frequency scaling period compared to the normalfrequency.

FIG. 10 is a diagram for describing a change in entire currentconsumption when memory devices coupled to a plurality of channels startoperations substantially at the same time in accordance with anembodiment. Referring to FIG. 10, if a plurality of memory devices startor end operations substantially at the same time, a noise may occur on avoltage source Vsource.

For example, the plurality of memory devices may remain idle until timet0. In the idle state, a total current I_(TOT) that is consumed in astorage device (e.g., the storage device 50 in FIG. 1) may be maintainedat a relatively low idle state current I_(IDLE). At a first time t0, theplurality of memory devices may start operations substantially at thesame time. As the plurality of memory devices start the operationssubstantially at the same time, the total current I_(TOT) that isconsumed in the storage device 50 during a period from the first time t0to a second time t1 may rapidly increase from the idle state currentI_(IDLE) to a peak current I_(PK). The total current I_(TOT) that hasincreased to the peak current I_(PK) at the second time t1 may bereduced to a steady state current I_(SS) from the second time t1 to athird time t2 as the operation of the storage device 50 is stabilized.The storage device 50 is in a transient state during a period from thefirst time t0 to the third time t2.

From the third time t2 after the transient state has been terminated,the storage device 50 may operate in a steady state. The total currentI_(TOT) that is consumed by the storage device 50 in the steady statemay be stably maintained at the steady state current I_(SS).

As illustrated in FIG. 10, in the case where the plurality of memorydevices included in the storage device 50 start operations substantiallyat the same time, the total current I_(TOT) that is consumed by thestorage device 50 in the transient state may rapidly increase to thepeak current I_(PK). If each of the plurality of memory devices operatesat a relatively high speed, the peak current I_(PK) may have arelatively large magnitude.

In a memory controller (e.g., the memory controller 200 in FIG. 1) inaccordance with an embodiment of the present disclosure, when a memorydevice in the storage device 50 starts an operation, an initialfrequency of a clock signal output may be controlled based on an idletime of the memory device. In the memory controller 200 in accordancewith an embodiment of the present disclosure, if the idle time of thememory device exceeds a threshold time, a clock signal to be output tothe memory device may be generated based on an initial frequency lessthan a normal frequency during an initial frequency scaling period. Ifthe initial frequency scaling period has passed and the process enters anormal operation period, the memory controller 200 may generate a clocksignal to be output to the memory device based on the normal frequency.Therefore, even if a plurality of memory devices start operationssubstantially at the same time, the entire current consumption of thestorage device 50 may be prevented from rapidly increasing by reducingthe initial operation frequency of the clock signal from the memorydevice during the initial frequency scaling period compared to thenormal frequency.

FIG. 11 is a block diagram illustrating a memory controller 200 inaccordance with an embodiment of the present disclosure.

Referring to FIG. 11, the memory controller 200 in accordance with anembodiment of the present disclosure may include an idle time monitor210 and a clock signal generator 230. The idle time monitor 210 maymonitor an idle time t_(IDLE) of the memory device included in a storagedevice (e.g., the storage device 50 in FIG. 1) and output it to theclock signal generator 230. For example, the idle time monitor 210 maygenerate a signal indicative the idle time t_(IDLE) of the memory deviceand output the generated signal to the clock signal generator 230. Theclock signal generator 230 may generate a read enable signal RE # or adata strobe signal DQS based on the received idle time t_(IDLE).

FIG. 12 is a block diagram illustrating the clock signal generator 230of FIG. 11 in accordance with an embodiment of the present disclosure.

Referring to FIG. 12, the clock signal generator 230 may include afrequency controller 231, a read enable signal generator 233, and a datastrobe signal generator 235.

The frequency controller 231 may receive an idle time t_(IDLE) of thememory device and control a frequency of a clock signal to be output tothe memory device. In other words, the frequency controller 231 maygenerate a frequency FR1 or FR2 for generating a clock signal andtransmit the frequency FR1 or FR2 to the read enable signal generator233 or the data strobe signal generator 235. For example, the frequencycontroller 231 may generate a first signal indicative of a firstfrequency FR1 and transmit the first signal to the read enable signalgenerator 233, or may generate a second signal indicative of a secondfrequency FR2 and transmit the second signal to the data strobe signalgenerator 235.

In more detail, during a read operation of the memory device, the memorycontroller 200 may generate a read enable signal RE #. In this case, thefrequency controller 231 may control the frequency FR1 for generatingthe read enable signal RE # based on the idle time t_(IDLE). During aprogram operation of the memory device, the memory controller 200 maygenerate a data strobe signal DQS. In this case, the frequencycontroller 231 may control the frequency FR2 for generating the datastrobe signal DQS based on the idle time t_(IDLE).

The read enable signal generator 233 may generate a read enable signalRE # based on the frequency FR1 that is controlled by the frequencycontroller 231. The data strobe signal generator 235 may generate a datastrobe signal DQS based on the frequency FR2 that is controlled by thefrequency controller 231.

An operation of the memory controller 200 in accordance with anembodiment of the present disclosure will be described below in detailwith reference to FIG. 13.

FIG. 13 is a flowchart for describing a method of operating a memorycontroller (e.g., the memory controller 200 in FIG. 11) in accordancewith an embodiment of the present disclosure.

Referring to FIG. 13, at step S110, an operation of a memory device thatis idle may be determined. At step S110, it may be determined that anoperation of at least one of the first to fourth memory devices 100_1 to100_4 illustrated in FIG. 8 starts. At step S110, it may be determinedthat an operation for at least one of the first to eighth memory devices100_1 to 100_8 illustrated in FIG. 9 starts.

At step S120, an idle time t_(IDLE) of a memory device that has beendetermined to start the operation may be determined. The idle timet_(IDLE) of the memory device may correspond to a time interval betweena first time when a previous operation of the corresponding memorydevice ends to a second time when a subsequent operation thereof starts.Step S120 may be performed by the idle time monitor 210 of FIG. 11.

At step S130, it is determined whether the determined idle time (or idletime interval) t_(IDLE) is greater than a threshold time (or a thresholdtime interval) t_(THR). The threshold time t_(THR) may be a value thatis determined depending on the design or a result of simulation. If thedetermined idle time t_(IDLE) is greater than the threshold timet_(THR), it may indicate that the memory device has been idle for arelatively long time. When the memory device that has been idle for arelatively long time starts an operation, there is high possibility forother memory devices to also start operations substantially at the sametime.

Therefore, if the idle time t_(IDLE) of the memory device is greaterthan the threshold time t_(THR) (YES at step S130), a clock signalneeded for the operation may be generated based on an initial frequencyFR_(IS) (at step S140). Hence, during an initial operation period of thememory device, the clock signal may be generated based on the initialfrequency FR_(IS). For example, the generated clock signal may have theinitial frequency FR_(IS) during the initial operation period. After theinitial operation period of the memory device, a clock signal may begenerated based on a normal frequency FR_(NM) (at step S150). Hence,during a normal operation period after the initial operation period ofthe memory device, the clock signal may be generated based on the normalfrequency FR_(NM). For example, the generated clock signal may have thenormal frequency FR_(NM) during a normal operation period. The initialfrequency FR_(IS) may be a value less than the normal frequency FR_(NM).Therefore, if the idle time t_(IDLE) of the memory device is greaterthan the threshold time t_(THR) (YES at step S130), the initialoperation may be performed based on the initial frequency FR_(IS) havinga value less than the normal frequency FR_(NM), and the normal operationmay be thereafter performed based on the normal frequency FR_(NM). Theoperation frequency of the memory device may have great influence oncurrent consumption. Hence, the peak current I_(PK) that occurs in atransient period t0 to t2 of FIG. 10 may be reduced.

If the determined idle time t_(IDLE) is equal to or less than thethreshold time t_(THR), it may indicate that the memory device has beenidle for a relatively short time. If the memory device that has beenidle for a relatively short time starts an operation, there is highpossibility for other memory devices each to keep performing currentoperations or remain in the idle state, rather than starting a newoperation. Therefore, if the idle time t_(IDLE) of the memory device isequal to or less than the threshold time t_(THR) (NO at step S130), theprocess may directly enter the normal operation period without theinitial operation period. Therefore, in this case, step S150 may bedirectly performed without performing step S140. Hence, the operatingspeed of the memory device may not be significantly reduced because ofan unnecessary initial operation.

FIGS. 14A and 14B are timing diagrams for describing a method ofoperating a memory controller (e.g., the memory controller 200 in FIG.11) in accordance with an embodiment of the present disclosure. AlthoughFIGS. 14A and 14B illustrate read enable signals RE # as examples of aclock signal, embodiments of the present disclosure are not limitedthereto. For example, a data strobe signal DQS which is generated by thememory controller 200 may also be illustrated in the same manner asillustrated in FIGS. 14A and 14B.

FIG. 14A shows a read enable signal RE # that is generated in a firstcase CASE I where the idle time t_(IDLE) is equal to or less than thethreshold time t_(THR) as a result of the determination at step S130 ofFIG. 13. The read enable signal RE # that has swung based on the normalfrequency FR_(NM) during a previous operation period may not swingduring an idle period. Since the idle time t_(IDLE) in the idle periodis less than the threshold time t_(THR), the idle period may end and anormal operation period may directly start. Specifically, the idle timet_(IDLE) may correspond to a duration of the idle period. During thenormal operation period, the read enable signal RE # may be generatedbased on the normal frequency FR_(NM) at step S150 of FIG. 13. Duringthe normal operation period, a data transfer operation may be performedbetween a memory device and a memory controller. In more detail, since aclock signal illustrated in FIG. 14A is a read enable signal RE #, readdata may be transmitted from the memory device to the memory controllerduring the normal operation period.

FIG. 14B shows a read enable signal RE # that is generated in a secondCASE II where the idle time t_(IDLE) is greater than the threshold timet_(THR) as a result of the determination at step S130. The read enablesignal RE # that has swung based on the normal frequency FR_(NM) duringa previous operation period may not swing during an idle period. Sincethe idle time t_(IDLE) in the idle period is greater than the thresholdtime t_(THR), the idle period may end and an initial operation period,i.e., an initial frequency scaling period, may start. During the initialfrequency scaling period, the read enable signal RE # may be generatedbased on a scaled initial frequency FR_(IS) at step S140 of FIG. 13. Theinitial frequency FR_(IS) may have a value less than the normalfrequency FR_(NM). Hence, during the initial frequency scaling period, aclock signal, e.g., a read enable signal RE #, may swing at a relativelylow speed.

If the initial operation period, i.e., the initial frequency scalingperiod, is terminated, the normal operation period may start. During thenormal operation period, the read enable signal RE # may be generatedbased on the normal frequency FR_(NM) at step S150. During the initialfrequency scaling period and the normal operation period, a datatransfer operation may be performed between the memory device and thememory controller. In more detail, since a clock signal illustrated inFIG. 14B is a read enable signal RE #, read data may be transmitted fromthe memory device to the memory controller during the initial frequencyscaling period and the normal operation period.

As illustrated in FIGS. 14A and 14B, when the memory device 100 startsan operation, the memory controller 200 in accordance with an embodimentof the present disclosure may control the initial frequency of a clocksignal output based on the idle time t_(IDLE) of the memory device 100.In the memory controller 200 in accordance with an embodiment of thepresent disclosure, if the idle time t_(IDLE) of the memory device 100exceeds the threshold time t_(THR), a clock signal to be output to thememory device 100 may be generated based on an initial frequency FR_(IS)less than the normal frequency FR_(NM) during the initial frequencyscaling period. If the initial frequency scaling period has passed andthe process enters a normal operation period, the memory controller maygenerate a clock signal to be output to the memory devices 100 based onthe normal frequency FR_(NM). Therefore, if the plurality of memorydevices 100_1 to 100_8 start operations substantially at the same time,the entire current consumption of the storage device 50 may be preventedfrom rapidly increasing by reducing the initial operation frequency.

Referring to FIG. 14B, the second case CASE II where the initialfrequency FR_(IS) used during the initial frequency scaling period is aninvariable constant. In other words, during the initial frequencyscaling period of FIG. 14B, the frequency of the read enable signal RE #may remain substantially constant. However, various embodiments of thepresent disclosure are not limited thereto. For example, the initialfrequency FR_(IS) that is used during the initial frequency scalingperiod may vary over time. For instance, the initial frequency FR_(IS)that is used during the initial frequency scaling period may begradually increased over time. Embodiments of controlling the frequencyof a clock signal generated during the initial frequency scaling periodwill be described with reference to FIGS. 15 to 18.

FIG. 15 is a flowchart illustrating step S140 of FIG. 13 in accordancewith an embodiment of the present disclosure. FIG. 15 illustrates anexample of a method of controlling the frequency of a clock signalgenerated during an initial frequency scaling period. In other words,FIG. 15 illustrates a method of controlling the initial frequencyFR_(IS) according to an embodiment.

Referring to FIG. 15, a frequency controller (e.g., the frequencycontroller 231 in FIG. 12) may set the initial frequency FR_(IS) to abasic frequency FR0 as an initial value at step S210. The basicfrequency FR0 may be a constant value and be less than the normalfrequency FR_(NM). Thereafter, at step S220, a clock signal isgenerated. Step S220 may be performed by a read enable signal generator(e.g., the read enable signal generator 233 in FIG. 12) or a data strobesignal generator (e.g., the data strobe signal generator 235 in FIG.12). At step S220, a clock signal corresponding to one cycle may begenerated. The clock signal may be a read enable signal RE # or a datastrobe signal DQS.

After the clock signal corresponding to one cycle has been generated atstep S220, it is determined whether clock signals have been generated bya given number of unit clocks at step S230. The number of unit clocksmay indicate the number of cycles of clocks that are sequentiallygenerated by the same initial frequency FR_(IS). In an embodiment, theclock signal is generated based on the same initial frequency FR_(IS)until the number of cycles of the generated clock signal reaches a givennumber. For example, in the case where the number of unit clocks isthree, clock signals having the same frequency may be generated duringthree cycles. The number of unit clocks may be set to various values, asneeded.

As a result of the determination at step S230, if clock signals are notgenerated by the number of unit clocks (NO at step S230), the processmay return to step S220 without changing the initial frequency FR_(IS)so that a clock signal corresponding to one cycle is generated again. Ifthe foregoing is repeated and clock signals are thus generated by thenumber of unit clocks (YES at step S230), the initial frequency FR_(IS)is increased at step S240. At step S240, the initial frequency FR_(IS)may increase by various increments.

After the initial frequency FR_(IS) is increased, it may be determinedwhether the initial frequency FR_(IS) has reached the normal frequencyFR_(NM) at step S250. If the initial frequency FR_(IS) has reached thenormal frequency FR_(NM) (YES at step S250), this may indicate that theinitial frequency scaling period has been terminated. Therefore,referring back to FIG. 13, step S140 may end, and the process mayproceed to step S150 so that the normal operation period may start.

If the initial frequency FR_(IS) has not reached the normal frequencyFR_(NM) (NO at step S250), the process may return to step S220 so that aclock signal corresponding to the increased initial frequency FR_(IS)may be generated.

FIGS. 16A and 16B are timing diagrams for describing the process of FIG.15 according to embodiments.

FIG. 16A illustrates a method of controlling the initial frequencyFR_(IS) in the case where the number of unit clocks is two. If theinitial frequency scaling period starts, the initial frequency FR_(IS)may be set to the basic frequency FR0, at step S210. Hence, during afirst unit clock period UC1, a clock signal (e.g., a read enable signalRE #) corresponding to two cycles may be generated based on the basicfrequency FR0.

If the clock signal corresponding to two cycles is generated, thefrequency controller 231 may increase the initial frequency FR_(IS) as aresult of the determination at step S230. Hence, during a second unitclock period UC2, a clock signal corresponding to two cycles may begenerated based on the increased initial frequency FR_(IS). Likewise,during a third unit clock period UC3, a clock signal may be generatedbased on a further increased initial frequency FR_(IS). During a fourthunit clock period UC4, a clock signal may be generated based on afurther increased initial frequency FR_(IS). In the case where thefourth unit clock period ends and the initial frequency FR_(IS) that hasincreased by step S240 has reached the normal frequency FR_(NM), theinitial frequency scaling period may end and the process may enter thenormal operation period.

FIG. 16B illustrates a method of controlling the initial frequencyFR_(IS) in the case where the number of unit clocks is one. Since thenumber of unit clocks is one, the read enable signal RE # may begenerated based on the initial frequency FR_(IS) that increases for eachperiod. In other words, since the unit clock period in FIG. 16B is aclock period corresponding to one cycle, the initial frequency FR_(IS)may increase at each time when the clock signal completes one cycle.

Although FIGS. 16A and 16B illustrate examples in which the numbers ofunit clocks are two and one, respectively, embodiments of the presentdisclosure are not limited thereto. For example, an embodiment in whichthe number of unit clocks is 3 or more may also fall within the boundsof the present disclosure.

FIG. 17 is a flowchart illustrating step S140 of FIG. 13 according to anembodiment. FIG. 17 illustrates an example of a method of controlling afrequency of a clock signal generated during an initial frequencyscaling period.

Referring to FIG. 17, a frequency controller (e.g., the frequencycontroller 231 in FIG. 12) may set the initial frequency FR_(IS) to abasic frequency FR0 as an initial value at step S310. The basicfrequency FR0 may be a constant value and be less than the normalfrequency FR_(NM). Thereafter, at step S320, a clock signal isgenerated. Step S320 may be performed by a read enable signal generator(e.g., the read enable signal generator 233 in FIG. 12) or a data strobesignal generator (e.g., the data strobe signal generator 235 in FIG.12). At step S320, a clock signal corresponding to one cycle may begenerated. The clock signal may be a read enable signal RE # or a datastrobe signal DQS.

After the clock signal corresponding to one cycle has been generated atstep S320, it is determined whether a clock signal has been generatedduring a unit time (or unit time interval) at step S330. The unit timemay indicate the time it takes to generate a clock signal having thesame initial frequency FR_(IS). For example, the unit time may be a timeinterval during which the clock signal is generated to have the sameinitial frequency FR_(IS) for a given number of periods. The unit timemay be set to various values, as needed.

As a result of the determination at step S330, if a duration duringwhich the clock signal has been generated is shorter than the unit time(NO at step S330), the process may return to step S320 without changingthe initial frequency FR_(IS) so that a clock signal corresponding toone cycle is generated again. For example, when the duration duringwhich the clock signal has been generated is shorter than the unit time,the process continues to generate the clock signal during a next cyclewhile keeping the initial frequency FR_(IS). The foregoing is repeated,and a clock signal is generated based on the same initial frequencyFR_(IS) until it reaches the unit time. For example, the processcontinues to generate the clock signal having the same initial frequencyFR_(IS) until the duration during which the clock signal has beengenerated reaches the unit time.

If a clock signal is generated during the unit time (YES at step S330),the initial frequency value FR_(IS) is increased, at step S340. At stepS340, the initial frequency FSIS may increase by various increments.

After the initial frequency FR_(IS) has increased, it is determinedwhether an initial operation time has passed at step S350. The initialoperation time may be a predetermined fixed time and be used todetermine the initial frequency scaling period. If the initial operationtime has passed (YES at step S350), this may indicate that the initialfrequency scaling period has ended. Therefore, referring back to FIG.13, step S140 may end, and the process may proceed to step S150 so thatthe normal operation period may start.

If the initial operation time has not yet passed (NO at step S350), theprocess may return to step S320 so that a clock signal corresponding tothe increased initial frequency FR_(IS) is generated.

FIG. 18 is a timing diagram for describing the process in FIG. 17according to an embodiment.

Referring to FIG. 18, there are illustrated a unit time UT and aninitial operation time IT. During the unit time UT, the initialoperation frequency FR_(IS) may remain substantially constant. Each timethe unit time UT passes, the initial operation frequency FR_(IS) isincreased. If the initial operation time IT passes, the initialfrequency scaling period ends, and the normal operation period starts.

Although FIGS. 15 to 18 illustrate embodiments of step S140 ofgenerating a clock signal based on the initial frequency FR_(IS),embodiments of the present disclosure are not limited thereto.Therefore, during the initial frequency scaling period, the initialfrequency FR_(IS) may be controlled not only by the methods described inthe embodiments of FIGS. 15 to 18 but also by various methods. Asdescribed with reference to FIGS. 15 to 18, the initial frequencyFR_(IS) may be controlled such that it is gradually increased during theinitial frequency scaling period. Referring back to FIG. 16A, the readenable signal RE # has a first initial frequency during the first unitclock period UC1, a second initial frequency during the second unitclock period UC2, a third initial frequency during the third unit clockperiod UC3, and a fourth initial frequency during the fourth unit clockperiod UC4. In an embodiment, the second initial frequency is a firstgiven times as great as the first initial frequency, the third initialfrequency is a second given times as great as the second initialfrequency, and the fourth initial frequency is a third given times asgreat as the third initial frequency. For example, each of the first,second, and third given times may be in a range from 1.1 times to 5times. The initial frequency FR_(IS) that is controlled during theinitial frequency scaling period may have a value that is always lessthan the normal frequency FR_(NM).

FIG. 19 is a flowchart illustrating step S140 of FIG. 13 according to anembodiment.

Referring to FIG. 19, step S140 of generating a clock signal needed toperform an operation based on the initial frequency FR_(IS) illustratedin FIG. 13 may include step S141 of generating a clock signal based on afirst initial frequency FR_(IS) less than the normal frequency FR_(NM),and the step S143 of generating a clock signal based on a second initialfrequency FR_(IS2) less than the normal frequency FR_(NM) and greaterthan the first initial frequency FR_(IS1).

Referring to FIGS. 14B, 16A, 16B, and 18, the initial frequency scalingperiod may be set to a single period. However, in a method of operatingthe memory controller in accordance with an embodiment of the presentdisclosure, the initial frequency scaling period may include two or moreperiods. Hereinafter, the embodiment of FIG. 19 will be described withreference to FIG. 20 together.

FIG. 20 is a timing diagram for describing the process illustrated inFIG. 19 according to an embodiment.

FIG. 20 shows a read enable signal RE # that is generated in the casewhere the idle time t_(IDLE) is greater than the threshold time t_(THR)as a result of the determination at step S130 of FIG. 13. The readenable signal RE # that has swung based on the normal frequency FR_(NM)during a previous operation period may not swing during an idle period.Since the idle time t_(IDLE) in the idle period is greater than thethreshold time t_(THR), the idle period ends and an initial operationperiod, i.e., an initial frequency scaling period, starts. During aninitial frequency scaling period including a first initial frequencyscaling period and a second initial frequency scaling period, the readenable signal RE # may be generated based on scaled first and secondinitial frequencies FR_(IS1) and FR_(IS2) at step S140 of FIG. 13.During the first initial frequency scaling period, the second initialfrequency scaling period, and a normal operation period, a data transferoperation may be performed between a memory device and a memorycontroller. In more detail, since a clock signal illustrated in FIG. 20is a read enable signal RE #, read data may be transmitted from thememory device to the memory controller during the first initialfrequency scaling period, the second initial frequency scaling period,and the normal operation period.

In an embodiment illustrated in FIG. 20, the initial frequency scalingperiod may include a first initial frequency scaling period and a secondinitial frequency scaling period. During the first initial frequencyscaling period, a read enable signal RE # may be generated based on thefirst initial frequency FR_(IS1) at step S141. The first initialfrequency FR_(IS1) may be a value less than the normal frequencyFR_(NM). During the second initial frequency scaling period, a readenable signal RE # may be generated based on the second initialfrequency FR_(IS2) at step S143. The second initial frequency FR_(IS2)may have a value less than the normal frequency FR_(NM) and greater thanthe first initial frequency FR_(IS1).

In an embodiment, the first initial frequency FR_(IS1) may have aconstant value. In this case, during the first initial frequency scalingperiod, the read enable signal RE # may be generated based on a constantfrequency less than the normal frequency FR_(NM). However, embodimentsof the present disclosure are not limited thereto. For example, thefirst initial frequency FR_(IS1) may have a value that is graduallyincreased during the first initial frequency scaling period.

In an embodiment, the second initial frequency FR_(IS2) may have a valuethat is gradually increased during the second initial frequency scalingperiod. In this case, the read enable signal RE # based on the secondinitial frequency FR_(IS2) may be generated in the same manner asdescribed with reference to FIGS. 15 to 18. However, embodiments of thepresent disclosure are not limited thereto. For example, the secondinitial frequency FR_(IS2) may have a constant value during the secondinitial frequency scaling period.

If the initial operation period including the first and second initialfrequency scaling periods is terminated, the normal operation period maystart. During the normal operation period, the read enable signal RE #may be generated based on the normal frequency FR_(NM) at step S150 ofFIG. 13.

As illustrated in FIGS. 19 and 20, when the memory device 100 starts anoperation, the memory controller 200 in accordance with an embodiment ofthe present disclosure may control the initial frequency of a clocksignal output based on the idle time t_(IDLE) of the memory device 100.In the memory controller 200 in accordance with an embodiment of thepresent disclosure, if the idle time t_(IDLE) of the memory device 100exceeds the threshold time t_(THR), a clock signal to be output to thememory device 100 may be generated based on the first and second initialfrequencies FR_(IS1) and FR_(IS2) that are less than the normalfrequency FR_(NM) during the first and second initial frequency scalingperiods. If the initial frequency scaling period has passed and theprocess enters a normal operation period, the memory controller 200 maygenerate a clock signal to be output to the memory devices 100 based onthe normal frequency FR_(NM). Therefore, if the plurality of memorydevices 100_1 to 100_8 start operations substantially at the same time,the entire current consumption of the storage device 50 may be preventedfrom rapidly increasing by reducing the initial operation frequency.

FIG. 21 is a flowchart illustrating a method of operating a memorycontroller in accordance with an embodiment of the present disclosure.FIG. 22 is a diagram for describing a method of determining an idle timeat steps S410 and S420 of FIG. 21 according to an embodiment. Referringto FIGS. 21 and 22 together, a frequency scaling operation may beperformed based on an idle time of one or more memory devices other thana memory device that starts an operation. Hereinafter, description willbe made with reference to FIGS. 21 and 22 together.

Referring to FIGS. 21 and 22, at step S410, an operation of a memorydevice selected from among a plurality of memory devices 100_1 to 100_4coupled to respective different channels CH1 to CH4 may be determined.Here, the selected memory device may be idle. Referring to FIG. 22,there is illustrated an example in which, at step S410, the first memorydevice 100_1 of the first to fourth memory devices 100_1 to 100_4 is theselected memory device. In FIG. 22, idle times of the first to fourthmemory devices 100_1 to 100_4 are illustrated as being respectivelyfirst to fourth idle times t_(IDLE)_1 to t_(IDLE_4). According to theembodiment illustrated in FIGS. 13 to 14B, the idle time t_(IDLE) atstep S120 of FIG. 13 may be determined to be the first idle timet_(IDLE)_1 of the first memory device 100_1 that is the selected memorydevice. According to the embodiment of FIGS. 21 and 22, the idle timet_(IDLE) may be determined based on an idle time of the unselectedmemory devices rather than the selected memory device. Since theselected memory device 100_1 has been idle, the first idle timet_(IDLE)_1 may have a value other than 0. If any one memory device ofthe second to fourth memory devices 100_2 to 100_4 is in operation, theidle time of the operating memory device may be determined to be 0.

At step S420, an idle time (or an idle time interval) t_(IDLE) of memorydevices including at least one unselected memory device among theplurality of memory devices may be determined. The unselected memorydevice may be a memory device other than the selected memory device. InFIG. 22, the at least one unselected memory device may include second tofourth memory devices 100_2 to 100_4. At step S420, an idle timet_(IDLE) of memory devices including at least one memory device amongthe second to fourth memory devices 100_2 to 100_4 may be determined.

In an embodiment, the idle time t_(IDLE) at step S420 may be determinedto be any one idle time among the second to fourth idle times t_(IDLE_2)to t_(IDLE_4).

In an embodiment, the idle time t_(IDLE) at step S420 may be determinedto be the sum of two idle times among the first to fourth idle timest_(IDLE)_1 to t_(IDLE_4).

In an embodiment, the idle time t_(IDLE) at step S420 may be determinedto be the sum of three idle times among the first to fourth idle timest_(IDLE)_1 to t_(IDLE_4).

In an embodiment, the idle time t_(IDLE) at step S420 may be determinedto be the sum of all of the first to fourth idle times t_(IDLE)_1 tot_(IDLE_4).

FIG. 23 is a flowchart illustrating a method of operating a memorycontroller in accordance with an embodiment of the present disclosure.FIG. 24 is a diagram for describing a method of determining an idle timeat steps S510 and S520 of FIG. 23 according to an embodiment. Referringto FIGS. 23 and 24 together, a frequency scaling operation may beperformed based on an idle time of memory devices other than a memorydevice that starts an operation. Hereinafter, description will be madewith reference to FIGS. 23 and 24 together. FIG. 24 shows an examplewhere two memory devices are coupled to each channel. In otherembodiments, three or more memory devices may be coupled to eachchannel. In the embodiment shown in FIG. 24, the first memory device100_1 is coupled to the first channel CH1 through a first way WAY1 andthe second memory device 100_2 is coupled to the first channel CH1through a second way WAY2. The first and second memory devices 100_1 and100_2 may be coupled to the memory controller 200 through the firstchannel CH1. The third memory device 100_2 is coupled to the secondchannel CH2 through a third way WAY3, and the fourth memory device 100_4is coupled to the second channel CH2 through a fourth way WAY4. Hence,the third and fourth memory devices 100_3 and 100_4 may be coupled tothe memory controller 200 through the second channel CH2.

Referring to FIGS. 23 and 24, at step S510, an operation of a memorydevice selected from among the plurality of memory devices 100_1 to100_8 coupled to the plurality of channels CH1 to CH4 and the respectivedifferent ways WAY1 to WAY8 may be determined. Here, the selected memorydevice may be idle. Referring to FIG. 24, there is illustrated anexample in which, at step S510, the first memory device 100_1 of thefirst to eighth memory devices 100_1 to 100_8 is the selected memorydevice. In FIG. 24, idle times of the first to eighth memory devices100_1 to 100_8 are illustrated as being respectively first to eighthidle times t_(IDLE)_1 to t_(IDLE_8). According to the embodimentillustrated in FIGS. 13 to 14B, the idle time t_(IDLE) at step S120 ofFIG. 13 may be determined to be the first idle time t_(IDLE)_1 of thefirst memory device 100_1 that is the selected memory device. Accordingto the embodiment of FIGS. 23 and 24, the idle time t_(IDLE) may bedetermined based on an idle time of an unselected memory device that iscoupled to the same channel as that of the selected memory device andcoupled to a way different from that of the selected memory device.Since the selected memory device 100_1 has been idle, the first idletime t_(IDLE_1) may have a value other than 0. If any one memory deviceof the second to eighth memory devices 100_2 to 100_8 is in operation,the idle time of the operating memory device may be determined to be 0.

At step S520, an idle time t_(IDLE) of memory devices including at leastone unselected memory device among the plurality of memory devices maybe determined. In this case, the idle time t_(IDLE) of memory devicesincluding the unselected memory device that is coupled to the samechannel as that of the selected memory device and to a way differentfrom that of the selected memory device may be determined. In FIG. 24,the unselected memory device that is coupled to the same channel CH1 asthat of the first memory device 100_1 and to a way WAY2 different fromthat WAY1 of the first memory device 100_1 may be the second memorydevice 100_2. At step S520, the idle time t_(IDLE) of the memory devicesincluding the second memory device 100_2 may be determined.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the second idle time t_(IDLE)_2.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of the first idle time t_(IDLE)_1 and the second idle timet_(IDLE)_2. In an embodiment, the idle time t_(IDLE) at step S520 may bedetermined to be the sum of the second idle time t_(IDLE)_2 and any oneof the third to eighth idle times t_(IDLE)_3 to t_(IDLE)_8.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of the second idle time t_(IDLE)_2 and any two of thefirst and the third to eighth idle times t_(IDLE)_1 and t_(IDLE)_3 tot_(IDLE)_8.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of the second idle time t_(IDLE)_2 and any three of thefirst and the third to eighth idle times t_(IDLE)_1 and t_(IDLE)_3 tot_(IDLE)_8.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of the second idle time t_(IDLE)_2 and any four of thefirst and the third to eighth idle times t_(IDLE)_1 and t_(IDLE)_3 tot_(IDLE)_8.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of the second idle time t_(IDLE)_2 and any five of thefirst and the third to eighth idle times t_(IDLE)_1 and t_(IDLE)_3 tot_(IDLE)_8.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of the second idle time t_(IDLE)_2 and any six of thefirst and the third to eighth idle times t_(IDLE)_1 and t_(IDLE)_3 tot_(IDLE)_8.

In an embodiment, the idle time t_(IDLE) at step S520 may be determinedto be the sum of all of the first to eighth idle times t_(IDLE)_1 tot_(IDLE)_8.

FIG. 25 is a diagram illustrating an example of the memory controller200 of FIG. 1.

A memory controller 1000 is coupled to a host and a memory device. Inresponse to a request from the host, the memory controller 1000 mayaccess the memory device. For example, the memory controller 1000 maycontrol a write operation, a read operation, an erase operation, and abackground operation of the memory device.

The memory controller 1000 may provide an interface between the memorydevice and the host. The memory controller 1000 may drive firmware forcontrolling the memory device.

Referring to FIG. 25, the memory controller 1000 may include a processor1010, a memory buffer 1020, an error correction code (ECC) circuit 1030,a host Interface 1040, a buffer controller 1050, a memory interface1060, and a bus 1070.

The bus 1070 may provide a channel between the components of the memorycontroller 1000.

The processor 1010 may control the overall operation of the memorycontroller 1000 and perform a logical operation. The processor 1010 maycommunicate with the external host through the host interface 1040 andcommunicate with the memory device through the memory interface 1060. Inaddition, the processor 1010 may communicate with the memory buffer 1020through the buffer controller 1050. The processor 1010 may control theoperation of the storage device by using the memory buffer 1020 as anoperating memory, a cache memory, or a buffer memory.

The processor 1010 may perform the function of a flash translation layer(FTL). The processor 1010 may translate a logical block address (LBA),provided by the host, into a physical block address (PBA) through theFTL. The FTL may receive the LBA and translate the LBA into the PBAusing a mapping table. An address mapping method using the FTL may bemodified in various ways depending on the unit of mapping.Representative address mapping methods may include a page mappingmethod, a block mapping method, and a hybrid mapping method.

The processor 1010 may randomize data received from the host. Forexample, the processor 1010 may use a randomizing seed to randomize datareceived from the host. Randomized data may be provided to the memorydevice as data to be stored, and may be programmed to the memory cellarray.

The processor 1010 may drive software or firmware to perform therandomizing operation or the derandomizing operation.

The memory buffer 1020 may be used as a working memory, a cache memory,or a buffer memory of the processor 1010. The memory buffer 1020 maystore codes and commands to be executed by the processor 1010. Thememory buffer 1020 may store data to be processed by the processor 1010.The memory buffer 1020 may include a static RAM (SRAM) or a dynamic RAM(DRAM).

The ECC circuit 1030 may perform error correction. The ECC circuit 1030may perform an ECC encoding operation based on data to be written to thememory device through the memory interface 1060. ECC encoded data may betransmitted to the memory device through the memory interface 1060. TheECC circuit 1030 may perform an ECC decoding operation on data receivedfrom the memory device through the memory interface 1060. For example,the ECC circuit 1030 may be included in the memory interface 1060 as acomponent of the memory interface 1060.

The host interface 1040 may communicate with the external host undercontrol of the processor 1010. The host interface 1040 may performcommunication using at least one of various communication methods suchas a universal serial bus (USB), a serial AT attachment (SATA), a serialattached SCSI (SAS), a high speed interchip (HSIC), a small computersystem interface (SCSI), a peripheral component interconnection (PCI), aPCI express (PCIe), a nonvolatile memory express (NVMe), a universalflash storage (UFS), a secure digital (SD), multi-media card (MMC), anembedded MMC (eMMC), a dual in-line memory module (DIMM), a registeredDIMM (RDIMM), and a load reduced DIMM (LRDIMM) communication methods.

The buffer controller 1050 may control the memory buffer 1020 undercontrol of the processor 1010.

The memory interface 1060 may communicate with the memory device undercontrol of the processor 1010. The memory interface 1060 may communicatea command, an address, and data with the memory device through thechannel. When the memory device included in the storage device (50 ofFIG. 1) starts an operation, the processor 1010 may control an initialoperation frequency based on the idle time of the corresponding memorydevice. In an embodiment, the processor 1010 may monitor the idle timeof the memory device included in the storage device (50 of FIG. 1) andupdate the monitored idle time to the memory buffer 1020. When thememory device that has been idle starts the operation, the processor1010 may determine the initial operation frequency based on the idletime stored in the memory buffer 1020. The memory interface 1060 maygenerate a clock signal to be transmitted to the memory device, based onthe initial operation frequency determined by the processor 1010.

Therefore, the idle time monitor 210 of FIG. 11 may be implemented asthe processor 1010 and the memory buffer 1020 of FIG. 25. The clocksignal generator 230 of FIG. 11 may be implemented as the memoryinterface 1060 of FIG. 25.

For example, the processor 1010 may control the operation of the memorycontroller 1000 by using codes. The processor 1010 may load codes from anonvolatile memory device (e.g., a read only memory) provided in thememory controller 1000. Alternatively, the processor 1010 may load codesfrom the memory device through the memory interface 1060.

For example, the bus 1070 of the memory controller 1000 may be dividedinto a control bus and a data bus. The data bus may transmit data in thememory controller 1000. The control bus may transmit control informationsuch as a command and an address in the memory controller 1000. The databus and the control bus may be separated from each other and may neitherinterfere with each other nor affect each other. The data bus may becoupled to the host interface 1040, the buffer controller 1050, the ECCcircuit 1030, and the memory interface 1060. The control bus may becoupled to the host interface 1040, the processor 1010, the buffercontroller 1050, the memory buffer 1020, and the memory interface 1060.

FIG. 26 is a block diagram illustrating a solid state drive (SSD) system3000 to which the storage device in accordance with an embodiment of thepresent disclosure is applied.

Referring to FIG. 26, the SSD system 3000 may include a host 3100 and anSSD 3200. The SSD 3200 may exchange signals SIG with the host 3100through a signal connector 3001 and may receive power PWR through apower connector 3002. The SSD 3200 may include an SSD controller 3210, aplurality of flash memories 3221 to 322 n, an auxiliary power supply3230, and a buffer memory 3240.

In an embodiment, the SSD controller 3210 may perform the function ofthe memory controller (200 of FIG. 1), described above with reference toFIG. 1.

The SSD controller 3210 may control the plurality of flash memories 3221to 322 n in response to the signals SIG received from the host 3100. Inan embodiment, the signals SIG may be signals based on an interfacebetween the host 3100 and the SSD 3200. For example, the signals SIG maybe signals defined by at least one of various interfaces such asuniversal serial bus (USB), multi-media card (MMC), embedded MMC (eMMC),peripheral component interconnection (PCI), PCI-express (PCI-E),advanced technology attachment (ATA), serial-ATA (SATA), parallel-ATA(PATA), small computer system interface (SCSI), enhanced small diskinterface (ESDI), integrated drive electronics (IDE), Firewire,universal flash storage (UFS), Wi-Fi, Bluetooth, and nonvolatile memoryexpress (NVMe) interfaces.

In an embodiment, when any one of the plurality of flash memories 3221to 322 n starts an operation, the SSD controller 3210 may control aninitial frequency of an output clock signal based on an idle timet_(IDLE) of the corresponding flash memory. In the case where the idletime t_(IDLE) of the corresponding flash memory exceeds the thresholdtime t_(THR), the SSD controller 3210 may generate a clock signal basedon an initial frequency FR_(IS) less than the normal frequency FR_(NM)during an initial frequency scaling period. If the initial frequencyscaling period has passed and the process enters a normal operationperiod, the SSD controller 3210 may generate a clock signal to be outputto the corresponding flash memory based on the normal frequency FR_(NM).Therefore, if the plurality of memory devices 3221 to 322 n startoperations at the same time, the entire current consumption of the SSDsystem 3000 may be prevented from rapidly increasing by reducing theinitial operation frequency.

The auxiliary power supply 3230 may be coupled to the host 3100 throughthe power connector 3002. The auxiliary power supply 3230 may besupplied with power PWR from the host 3100, and may be charged by thepower PWR. The auxiliary power supply 3230 may supply the power of theSSD 3200 when the supply of power from the host 3100 is not smoothlyperformed. In an embodiment, the auxiliary power supply 3230 may bepositioned inside the SSD 3200 or positioned outside the SSD 3200. Forexample, the auxiliary power supply 3230 may be disposed in a main boardand may supply auxiliary power to the SSD 3200.

The buffer memory 3240 functions as a buffer memory of the SSD 3200. Forexample, the buffer memory 3240 may temporarily store data received fromthe host 3100 or data received from the plurality of flash memories 3221to 322 n or may temporarily store metadata (e.g., a mapping table) ofthe flash memories 3221 to 322 n. The buffer memory 3240 may includevolatile memories such as DRAM, SDRAM, DDR SDRAM, LPDDR SDRAM, and GRAMor nonvolatile memories such as FRAM, ReRAM, STT-MRAM, and PRAM.

FIG. 27 is a block diagram illustrating a user system 4000 to which thestorage device in accordance with an embodiment of the presentdisclosure is applied.

Referring to FIG. 27, the user system 4000 may include an applicationprocessor 4100, a memory module 4200, a network module 4300, a storagemodule 4400, and a user interface 4500.

The application processor 4100 may run components included in the usersystem 4000, an operating system (OS) or a user program. In anembodiment, the application processor 4100 may include controllers,interfaces, graphic engines, etc. for controlling the componentsincluded in the user system 4000. The application processor 4100 may beprovided as a system-on-chip (SoC).

In an embodiment, when any one of a plurality of memory devices includedin the storage module 4400 starts an operation, the applicationprocessor 4100 may control an initial frequency of a clock signal to beoutput to a channel the application processor 4100 and the correspondingmemory device, based on an idle time t_(IDLE) of the correspondingmemory device. In the case where the idle time t_(IDLE) of thecorresponding memory device exceeds the threshold time t_(THR), theapplication processor 4100 may output a generated clock signal to thechannel between the application processor 4100 and the correspondingmemory device, based on an initial frequency FR_(IS) less than thenormal frequency FR_(NM) during an initial frequency scaling period. Ifthe initial frequency scaling period has passed and the process enters anormal operation period, the application processor 4100 may output agenerated clock signal to the channel between the application processor4100 and the corresponding memory device based on the normal frequencyFR_(NM). Therefore, if the plurality of memory devices included in thestorage module 4400 start operations at the same time, the entirecurrent consumption of the user system 4000 may be prevented fromrapidly increasing by reducing the initial operation frequency.

The memory module 4200 may function as a main memory, a working memory,a buffer memory, or a cache memory of the user system 4000. The memorymodule 4200 may include a volatile RAM such as a DRAM, an SDRAM, a DDRSDRAM, a DDR2 SDRAM, a DDR3 SDRAM, an LPDDR SDARM, an LPDDR2 SDRAM, andan LPDDR3 SDRAM, or a nonvolatile RAM such as a PRAM, a ReRAM, an MRAM,and an FRAM. In an embodiment, the application processor 4100 and thememory module 4200 may be packaged based on package-on-package (POP) andmay then be provided as a single semiconductor package.

The network module 4300 may communicate with external devices. Forexample, the network module 4300 may support wireless communication,such as code division multiple access (CDMA), global system for mobilecommunication (GSM), wideband CDMA (WCDMA), CDMA-2000, time divisionmultiple access (TDMA), long term evolution (LTE), WiMAX, WLAN, UWB,Bluetooth, or WI-FI communication. In an embodiment, the network module4300 may be included in the application processor 4100.

The storage module 4400 may store data therein. For example, the storagemodule 4400 may store data received from the application processor 4100.Alternatively, the storage module 4400 may transmit the data stored inthe storage module 4400 to the application processor 4100. In anembodiment, the storage module 4400 may be implemented as a nonvolatilesemiconductor memory device, such as a phase-change RAM (PRAM), amagnetic RAM (MRAM), a resistive RAM (RRAM), a NAND flash memory, a NORflash memory, or a NAND flash memory having a three-dimensional (3D)structure. In an embodiment, the storage module 4400 may be provided asa removable storage medium (i.e., removable drive), such as a memorycard or an external drive of the user system 4000.

In an embodiment, the storage module 4400 may include a plurality ofnonvolatile memory devices, and each of the plurality of nonvolatilememory devices may be operated in the same manner as that of the memorydevice described above with reference to FIG. 10. The storage module4400 may be operated in the same manner as that of the storage device 50described above with reference to FIG. 1.

The user interface 4500 may include interfaces for inputting data orinstructions to the application processor 4100 or outputting data to anexternal device. In an embodiment, the user interface 4500 may includeuser input interfaces such as a keyboard, a keypad, a button, a touchpanel, a touch screen, a touch pad, a touch ball, a camera, amicrophone, a gyroscope sensor, a vibration sensor, and a piezoelectricdevice. The user interface 4500 may further include user outputinterfaces such as an a Liquid Crystal Display (LCD), an Organic LightEmitting Diode (OLED) display device, an Active Matrix OLED (AMOLED)display device, an LED, a speaker, a monitor, and so on.

Various embodiments of the present disclosure may provide a memorycontroller capable of sequentially increasing or reducing the totalcurrent that is consumed in a plurality of memory devices, and a methodof operating the memory controller.

Examples of embodiments have been disclosed herein, and althoughspecific terms are employed, they are used and are to be interpreted ina generic and descriptive sense only and not for purpose of limitation.In some instances, as would be apparent to one of ordinary skill in theart as of the filing of the present application, features,characteristics, and/or elements described in connection with aparticular embodiment may be used singly or in combination withfeatures, characteristics, and/or elements described in connection withother embodiments unless otherwise specifically indicated. Accordingly,it will be understood by those of skill in the art that various changesin form and details may be made without departing from the spirit andscope of the present disclosure as set forth in the following claims.

What is claimed is:
 1. A memory controller configured to control amemory device, the memory device being coupled to the memory controllerthrough a channel, the memory controller comprising: an idle timemonitor configured to output an idle time interval of the memory device,the idle time interval being between an end time of a previous operationof the memory device and a start time of a current operation; and aclock signal generator configured to generate a clock signal based onthe idle time interval and output the clock signal to the memory devicethrough the channel to perform the current operation, wherein the clocksignal generator determines whether to apply an initial frequency togenerate the clock signal during an initial frequency scaling period ofthe current operation, based on a comparison result of the idle timeinterval with a threshold time interval.
 2. The memory controlleraccording to claim 1, wherein the clock signal generator comprises: afrequency controller configured to determine a frequency for generatingthe clock signal based on the idle time interval; and a signal generatorconfigured to generate the clock signal based on the determinedfrequency.
 3. The memory controller according to claim 2, wherein, whenthe idle time interval is greater than the threshold time interval: thefrequency controller determines the initial frequency for generating theclock signal during the initial frequency scaling period, and a normalfrequency for generating the clock signal during a normal operationperiod, during the initial frequency scaling period, the signalgenerator generates the clock signal based on the initial frequency; andduring the normal operation period after the initial frequency scalingperiod, the signal generator generates the clock signal based on thenormal frequency.
 4. The memory controller according to claim 3, whereina value of the initial frequency is less than a value of the normalfrequency.
 5. The memory controller according to claim 4, wherein thefrequency controller gradually increases the initial frequency duringthe initial frequency scaling period.
 6. The memory controller accordingto claim 4, wherein the initial frequency has a constant value duringthe initial frequency scaling period.
 7. The memory controller accordingto claim 2, wherein, when the idle time interval is equal to or lessthan the threshold time interval: the frequency controller determines anormal frequency; and the signal generator generates the clock signalbased on the normal frequency.
 8. The memory controller according toclaim 2, wherein the signal generator generates a read enable signal ora data strobe signal as the clock signal.
 9. The memory controlleraccording to claim 3, wherein the initial frequency scaling periodincludes a first initial frequency scaling period and a second initialfrequency scaling period, wherein the frequency controller determines afirst initial frequency for generating the clock signal during the firstinitial frequency scaling period and a second initial frequency forgenerating the clock signal during the second initial frequency scalingperiod, wherein, during the first initial frequency scaling period, thesignal generator generates the clock signal based on the first initialfrequency, the first initial frequency being less than the normalfrequency, and wherein, during the second initial frequency scalingperiod, the signal generator generates the clock signal based on thesecond initial frequency, the second initial frequency being less thanthe normal frequency and greater than the first initial frequency. 10.The memory controller according to claim 9, wherein the first initialfrequency has a constant value during the first initial frequencyscaling period, and wherein the second initial frequency graduallyincreases during the second initial frequency scaling period.
 11. Astorage device comprising: a plurality of memory devices; and a memorycontroller coupled with the plurality of memory devices through aplurality of channels and configured to control the plurality of memorydevices, wherein, when a single memory device among the plurality ofmemory devices starts an operation, the memory controller determineswhether to apply an initial frequency scaling to a clock signal based ona comparison result of an idle time interval of the memory device with athreshold time interval, and outputs the clock signal to the memorydevice.
 12. The storage device according to claim 11, wherein, when theidle time interval is greater than the threshold time interval, thememory controller generates the clock signal based on a first frequencyduring an initial operation period, and generates the clock signal basedon a second frequency greater than the first frequency during a normaloperation period after the initial operation period.
 13. The storagedevice according to claim 12, wherein the first frequency is maintainedat a constant value during the initial operation period.
 14. The storagedevice according to claim 12, wherein the first frequency increasesduring the initial operation period.
 15. The storage device according toclaim 11, wherein the clock signal is any one of a read enable signaland a data strobe signal.
 16. A method of operating a memory controller,the method comprising: determining to start an operation of a memorydevice; determining an idle time interval of the memory device;determining whether to apply an initial frequency scaling based on acomparison result of the idle time interval with a threshold timeinterval; and generating a clock signal based on a determination resultof whether to apply the initial frequency scaling to output the clocksignal to the memory device during the operation of the memory device.17. The method according to claim 16, wherein determining whether toapply the initial frequency scaling comprises: determining to apply theinitial frequency scaling, when the idle time interval is greater thanthe threshold time interval, and wherein generating the clock signalbased on the determination result of whether to apply the initialfrequency scaling comprises: in response to the comparison resultindicating that the idle time interval is greater than the thresholdtime interval, generating the clock signal based on an initialfrequency; and generating the clock signal based on a normal frequency,the normal frequency being greater than the initial frequency.
 18. Themethod according to claim 17, wherein generating the clock signal basedon the initial frequency comprises generating the clock signal based onthe initial frequency having a constant value.
 19. The method accordingto claim 17, wherein generating the clock signal based on the initialfrequency comprises generating the clock signal based on the initialfrequency having a value that gradually increases.
 20. The memorycontroller according to claim 1, wherein the initial frequency scalingperiod starts when the idle time interval ends, the clock signal havingthe initial frequency during the initial frequency scaling period, theinitial frequency being different from a normal frequency of the clocksignal.